This study assessed the environmental dynamics of pesticides in the São Lourenço River headwaters, Mato Grosso State, Brazil. The pesticides atrazine, flutriafol, metolachlor, α- and β-endosulfan and the metabolites endosulfan sulfate, desethylatrazine and desisopropylatrazine were determined in water (rain, surface, ground and runoff) and in sediment (runoff and bottom) samples, collected from August 2009 to July 2010, by SPE-GC/MS-SIM (solid phase extraction-gas chromatography/mass detector with selected ion monitoring). Runoff and rain atmospheric deposition showed to be important pathways for surface water contamination mainly by highly sorbed pesticides found in sediment with maximum concentration of 2218 μg kg-1 for β-endosulfan, and in water with maximum concentration of 28.3 μg L-1 for atrazine. Endosulfan sulfate, atrazine and metolachlor were the compounds with the highest frequency of detection. Leaching was an important process of off-site transport mainly due to the hydric behavior of soil and the low depth of water table, leading to contamination of groundwater as well as surface water via subsurface flow.
pesticide; runoff; leaching; off-site transport; water contamination
